非对称顶推力作用下盾构隧道结构响应研究

Responses of shield tunnel structure under action of asymmetric thrust

为研究盾构在小半径曲线隧道施工时非对称顶推力对隧道结构力学性能的影响,以广东圭峰山隧道区间盾构隧道为工程背景,考虑隧道衬砌材料的非线性特性,基于混凝土损伤塑性本构模型,建立盾构隧道施工阶段精细化有限元模型,采用数值方法分析了非对称顶推力作用下盾构隧道的力学特性。研究结果表明:①在非对称推力作用下盾尾衬砌管片横断面变形表现为向大荷载侧的挤出变形,非对称推力的影响范围与推力偏差量相关。②非对称推力引起的隧道竖向和横向弯矩远大于环向弯矩,其对环向内力影响较小,且主要体现为对环向剪力的影响。③盾构推进油缸的推力偏差使得隧道纵向由全断面受压状态逐渐过渡到压弯状态,在大推力侧的盾尾衬砌环缝(尤其是“T”形缝)间产生了明显的压应力集中,若该区域存在拼装误差,极易造成管片混凝土压溃;而小推力侧的纵向螺栓随着各组油缸推力偏差的增大开始受拉,使得部分环缝处于纵向受拉状态,存在潜在的环缝防水失效风险。因此,进行盾构曲线掘进施工时,应合理调配各组油缸推力,严格控制盾构衬砌管片拼装质量,同时应加强盾尾附近衬砌接缝的渗漏水监测。

To investigate the effects of asymmetric shield thrust on the mechanical properties of a tunnel structure during small radius curved advancing,a refined finite element model of the shield tunnel in Guifeng Mountain was established.The numerical model employed a damaged plastic constitutive model of concrete considering the nonlinear properties of the segmental lining.The mechanical behavior of the shield tunnel under asymmetric thrust was systematically analyzed using the established numerical model.The results showed that:①the cross-sectional deformation of the segment adjacent to the tail of the shield exhibits extrusion deformation towards the heavy load side under asymmetric thrust;②the vertical and transverse bending moments,induced by the asymmetric thrust,on the shield tunnel are much larger than those along the circumferential direction.Additionally,the influence of asymmetric thrust on the circumferential shear force on the tunnel is significant.③the mechanical state of the shield tunnel along the longitudinal direction is transferred from a whole-section compression state to a compression-bending state thanks to the pressure difference between different thrust jacks.A dramatic concentration of compressive stress occurs at the circumferential joints of segmental rings on the side with larger thrust,particularly at the T-shaped joints.The concrete of the segmental lining can easily crack in this area if there are assembly errors in the segments.Additionally,the longitudinal bolts embedded in the circumferential joint on the side with smaller thrust will gradually be in tension as the pressure difference among the thrust jacks increases.This keeps some circumferential joints in a state of tension,leading to a potential risk of waterproof failure in the shield tunnel.Therefore,when a shield drives along a curved alignment,the pressure of the different thrust jacks should be adjusted rationally,the assembly quality of the segmental lining should be strictly controlled,and the monitoring of seepage in the joints of the shield tunnel should be enhanced.